In recent years, in order to use oil discharged from an oil pump for apparatuses requiring different discharge pressures, for example, each sliding part of an engine, a variable valve actuation device configured to control operating characteristics of engine valves, and the like, there is a demand for two-stage characteristics, namely, a low pressure characteristic and a high pressure characteristic.
To satisfy such a demand, a variable-capacity oil pump, for instance as disclosed in the following Patent document 1, is provided with an eccentric ring that moves against a spring biasing force so as to change its eccentricity with respect to a rotor, and an electromagnetic valve for switching the direction of action of discharge pressure. The directional switching control is made via the electromagnetic valve so as to enable pump discharge pressure to act on the eccentric ring in a direction in which the eccentricity decreases or in a direction in which the eccentricity increases.
Also, in the aforementioned variable-capacity oil pump, an oil filter is disposed downstream of a main oil gallery or upstream of the electromagnetic valve, for preventing contaminants, such as metal debris in the oil, from being bitten into the electromagnetic valve.